The present invention relates generally to the field of elevators, and, more particularly, to the field of lighting for elevator cabs.
Lighting assemblies conventionally available for elevator cabs use overhead or ceiling-mounted lighting fixtures. There are several disadvantages associated with conventional lighting assemblies.
Conventional lighting assemblies typically require 4 to 10 inches of extra cab height to accommodate the light fixtures and the diffuser devices used to scatter the light evenly throughout the cab. The assemblies require additional structural components in the ceiling of the cab to carry the weight of the assemblies. The additional structural components add to the overall size and weight of elevator car, which can be very undesirable, especially in modernizing existing elevators. The administrative codes governing elevator modernization often place very tight restrictions on the weight of replacement elevator parts (including the cab) used in the modernization.
Conventional lighting assemblies are easily accessible to the passengers within the cab and exposed to vandalism or inadvertent damage. If broken, shards of glass or other components of the fixture may fall into the interior of the elevator cab and injure passengers. Replacing and repairing broken components on conventional lighting assemblies is often expensive and time-consuming.
The invention overcomes the problems associated with conventional lighting assemblies for elevators by providing a novel elevator cab lighting assembly that uses a refractive sheet to provide a diffuse, glare-free light within the interior of the elevator cab. The invention also comprises elevator cabs containing such lighting assemblies.
The lighting assembly of the invention comprises a refractive sheet having opposed planar surfaces, an inner edge, and an outer edge. The sheet is mounted on the cab and has a portion exposed to the interior of the elevator cab. A light source is mounted at and conducts light into the outer edge of the sheet. Light transmitted from the outer edge refracts randomly and internally along the longitude of the sheet and passes through the portion exposed to the interior of the elevator cab.
The refractive sheet can be formed from any suitable material which would provide a diffuse, glare-free light within the interior of the elevator cab. In one embodiment, the refractive sheet comprises acrylic. However, any clear or translucent material may be used. For example, the sheet may also comprise other plastics or glass. Although a preferred thickness for the refractive sheet is about 0.250 inches, the sheet can vary in thickness or material provided its structural integrity is maintained when the elevator is in operation, and it emits the desired amount of light into the cab. The portion of the sheet exposed to the interior of the cab may include the inner edge of the sheet or may also include an area along one of the planar surfaces. The sheet may be a variety of shapes, such as a rectangle, a semi-circle, a spline, or any other linear or curved shape.
One of the planar surfaces may be randomly sanded or sandblasted. One of the planar surfaces may also be etched or routed. The etching or routing may be in standard or custom designs to provide accent highlighting. The sheet may also include a mirrored layer (or a polished metal foil) or a painted layer on one of the planar surfaces. The inner edge may also contain a mirrored layer to reflect light back into the portion bounded by planar surfaces and thus enhance the intensity of light passing through the portion exposed to the interior of the elevator cab.
The sheet typically will be mounted on a ceiling surface of the cab, but it may also be mounted on other surfaces within the cab, such as a wall or floor surface.
In a preferred embodiment, the lighting assembly also includes a transom assembly for housing the outer edge and the light source. The transom assembly also contains a guide for enhancing conduction of light into the outer edge. The transom assembly may be mounted on the interior or exterior of the cab. When mounted on the exterior of the cab, the transom assembly actually defines the upper front comer section of the cab and intrudes into the space or ceiling height of the cab.
The transom assembly preferably includes a perforated face plate for being exposed to the interior of the cab and for diffusing light from the light source into the cab. The perforations of the face plate can be in the form of holes, gratings, grill bars, a plurality of slots or other light transmitting features. The face plate is of a sturdy configuration and is resistant to tampering and other forms of damage. In this case, the transom includes a lens mounted between the light source and the face plate. In addition, the inner edge is preferably aligned with the face plate and is disposed just above the top of the face plate.
The invention provides effective illumination of an elevator cab from a space saving lighting assembly. The invention is designed so as to meet the elevator code for adequate cab illumination. The code requires at least 5 foot candles power intensity at the threshold of the elevator with the doors closed.